In the related art, a hat type reinforcing member made of a composite material is known as a composite structure having a corner part (for example, refer to PTL 1). The hat type reinforcing member made of a composite material includes a hat section made of a composite material, a plurality of reinforcing plies made of a composite material joined to the hat section made of a composite material, and a noodle-like corner filler. The noodle-like corner filler is arranged in a substantially triangular noodle-like corner filler region formed by the plurality of reinforcing plies made of a composite material.